1. Field of the Invention
This invention relates to an apparatus for detecting moisture on a substrate, and in particular, to a moisture sensor positioned on a windshield that senses moisture to actuate a windshield wiper motor.
2. Technical Considerations
When operating a vehicle, it is important to maintain a clear, undistorted viewing area through the windshield of the vehicle. Windshield wiper mechanisms are provided to clear selected portions of the windshield of water and/or dirt that may obscure the vehicle operator's vision.
Moisture sensors have been used to sense rain on windshields and automatically actuate a windshield wiper motor to remove the water and clear the vision area. Some of these sensors include electrically conductive members having a protective coating on the exterior surface of the windshield. The conductive members are generally arranged in a fixed relationship to form variable capacitors whose output varies as a function of moisture absorbed by the overlaying protective coating. Other sensors use multiple pairs of conductive members and sequentially monitor the capacitance between the different pairs to determine the presence of moisture on the sensor.